This invention generally relates to electric discharge lamps and has particular reference to a fluorescent lamp component and a fluorescent lamp unit that are suitable for use as compact light sources in various kinds of residential and commercial lighting fixtures that are designed for incandescent type lamps.
Electric discharge lamps having tubular envelopes which provide "three-dimensional" type light sources are generally well known in the art. For example, a fluorescent lamp unit of helical configuration that is formed by coupling several semi-circular lamps together is disclosed in U.S. Pat. No. 2,652,483 granted Sept. 15, 1953 to Laidig et al. Another type of tridimensional fluorescent lamp that is formed by joining several conventional tubular fluorescent lamps in "bundled" configuration and interconnecting them with suitable apertures in the tube walls is disclosed in U.S. Pat. No. 3,501,662 issued Mar. 17, 1970 to Plagge.
Discharge lamps which have tubular envelopes that are bent into various shapes to provide concentrated light sources are also known in the art. British Pat. No. 854,745 published Nov. 23, 1960 discloses a double-ended sodium-vapor discharge lamp (FIGS. 3 and 4) having a tubular envelope that is bent upon itself twice to provide three straight tubular segments that are disposed in parallel triangular-spaced relationship. A luminous discharge tube having an envelope that is formed from glass tubing which is bent upon itself eleven times to provide a corresponding number of U-shaped sections is disclosed in U.S. Pat. No. 1,898,615 granted Feb. 21, 1933 to Byrnes. A fluorescent lamp having a tubular envelope that is bent upon itself three times to provide three conjoined U-shaped sections is disclosed in Japanese Design Patent No. 437,860 granted Sept. 20, 1976 to Y. Takeda et al. A lighting unit consisting of a heat-conserving housing that encloses a gaseous discharge lamp having a tubular envelope which is also bent upon itself three times to provide three U-bends and four straight sections is disclosed in U.S. Pat. Nos. 2,001,511 and 2,200,940 granted to Uyterhoeven et al. A compact screw-in type fluorescent lamp unit having a partitioned cylindrical envelope or a tubular envelope that is bent upon itself to provide a U-shaped or a generally M-shaped envelope (FIG. 5 embodiment) is disclosed in U.S. Pat. No. 3,551,736 granted Dec. 29, 1970 to Doehner.
Fluorescent lamp units of various designs that also have screw-type bases and are adapted to be used in lighting fixtures in place of incandescent lamps have also been proposed in the prior art. A lamp unit of this kind having adapter means which accommodates a conventional straight tubular double-ended fluorescent lamp and contains a ballast transformer that is located within a threaded base member is disclosed in U.S. Pat. No. 3,815,080 granted June 4, 1974 to F. Summa. U.S. Pat. Nos. 3,899,712 to Witting and 3,953,761 to LoGiudice disclose other types of screw-in fluorescent lamp units that are provided with integral ballast means or circuit components.
A method of making a circular-shaped fluorescent lamp by bending a heat-softened tubular glass envelope around a curved jig is disclosed in U.S. Pat. No. 3,993,465 granted Nov. 23, 1976 to Hurx et al.